In a metal-air battery, oxygen in the atmosphere is used as a positive-electrode active material to perform redox reaction of this oxygen at an air electrode that is a positive electrode. On the other hand, redox reaction of metal is performed at a metal electrode that is a negative electrode. The metal-air battery has a high energy density, thus being expected as a role such as an emergency power supply at the time of disaster or the like. This metal-air battery, which is expected as the role such as the emergency power supply or the like, is configured of a plurality of metal-air battery cells typically corresponding to a desired electricity output, and an injection of an electrolyte into each of the metal-air battery cells starts an electric generation.
Coupling and unitizing the plurality of metal-air battery cells ensures obtaining a desired output. The following patent documents disclose structures of battery units Japanese Patent Publication No. 2013-214472, Japanese Patent Publication No. 2013-214473 and Japanese Patent Publication No. S62-177873.